UAV-Mounted IRS-Enhanced Secondary Transmission and Primary Covert Communication for Cognitive Radio Networks

Abstract

A win-win scheme is investigated for uncrewed aerial vehicle-mounted intelligent reflecting surface (UIRS) enhanced secondary network (SN) data transmission and the primary network (PN) covert communication cooperative cognitive radio networks (UIRS-CCCRNs), where the moving UIRS can flexibly help SN to share the PN’s licensed spectrum and assist PN to hide its wireless transmission behavior. Based on this protocol, a SN’s average rate maximization problem is established under the imperfect channel state information (CSI), while ensuring the PN’s covert communication and weakening the warden’s detection capability. To solve the non-convexity and computational challenges, the original problem is decoupled into three subproblems, and the triangle inequality and the Cauchy-Schwarz inequality are employed to handle the CSI uncertainty. For both the SN’s transmit beamforming and the UIRS’s phase shift matrix subproblems, their optimal solution can be obtained by applying a low-complexity penalty dual decomposition with gradient projection (PDDGP) algorithm. Then, the non-convex UIRS’s trajectory subproblem is tackled by the successive convex approximation. Finally, an efficient joint trajectory and beamforming design that employs the PDDGP algorithm integrated into the block-coordinate-descent framework is proposed to obtain a suboptimal solution of the original problem. Simulation results demonstrate that by exploiting the UIRS, the proposed scheme flexibly assists the SN’s data transmission and PN’s covert communications, thereby achieving a win-win outcome for both PN and SN.